Energy and Recycling
PURPOSE
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Compare energy costs of recycling aluminum for cans to making cans from raw materials
Investigate extrinsic benefits and disadvantages of recycling, such as environmental and economic factors
BACKGROUND
The county government in one eastern state initiated an aluminum recycling program. Most of the aluminum is in
the form of beverage cans. In the first year, the county collected 1.4 x 10 6 kg of cans. It takes about 65 modern aluminum cans to make a kilogram.
All communities in the county have curb-side pickup of recycled materials. On average, each truck makes a 75-km
trip to pick up 3,500 kg of aluminum and gets 5 km/L fuel economy. Each liter of fuel produces
42,000 kJ energy.
EXERCISES
Show all your work.
1.
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5.
How many cans did the county collect in the first year?
To the nearest whole number, how many trips were needed to collect all the cans?
Calculate how many liters of fuel the trucks used to pick up the cans.
How many kilojoules (KJ) of energy were consumed collecting the cans?
Making cans from recycled aluminum requires about 180 kJ of energy per can. Calculate the total energy needed to
make cans from recycled aluminum, including the energy used to collect them.
6. It takes 1,520 kj of energy to make one aluminum can from bauxite ore. Assuming no other energy is used, calculate
how much energy is needed to make the cans from bauxite ore.
7. Calculate the energy difference between the two methods. How many liters of fuel are saved by recycling the cans?
PROBLEMS
Apparently, there is a considerable energy savings in using recycled aluminum to make new cans. The decision to
recycle is surely not that simple. There are many other factors to take into account.
8.
Describe two environmental and two economic problems associated with the recycling of aluminum.
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9.
There are many materials that lend themselves to recycling. Some of these do not have the clear-cut, easyto-see advantage of recycling aluminum. Take glass for example. To make glass from raw materials
requires a little over 18,100 kJ/kg of glass manufactured. To make glass from recycled materials takes
about 16,700 kJ/kg of glass product. If the costs of collecting the recycled glass are factored in, the energy
savings are more than offset.
Cite two environmental and two economic reasons to manufacture glass from recycled materials, even if the costs
are higher than from using raw materials.
10. Paper or plastic? Since the 1980s grocery shoppers have had that choice. Many customers selected paper, correctly
thinking that it is made of natural, renewable, environmentally friendly materials. The polyethylene plastic bags
were made from nonrenewable crude oil. As usual, the choice is not as clear-cut as it seems.
a.
Compare the manufacture, use, and reuse potential of paper versus plastic grocery bags. Investigate the
manufacture of each for: air pollution, water pollution, solid waste, energy use, land use and cost.
b. Other factors to consider: landfill volume, water pollution energy use land use ease of recycling
biodegradability
c. Explain two alternatives to paper or plastic grocery bags.